The relationship between subjective reactions to music and EEG frequencies over left and right occipital sites was studied in groups of musicians and nonmusicians. Selfreports of atten tiveness during music listening, familiarity with the music, and emotional reactions to the music all correlated moderately to substantially with various EEG frequency measures. The majority of significant correlations were between selfreports and direct measures of EEG activity in the slower theta and delta bands, while music minus silence EEG measures in the alpha and beta bands provided superior correlates of subjective reactions. These results suggest that EEG techniques may be useful in increasing understanding of brain mechanisms associated with music perception, and that it may prove to be ultimately possible to account for sizable segments of the variance of aesthetic reactions to musical stimuli in terms of EEG measures of brain activity.

Since the initial description of human brainwaves (Berger, 1929), there have been numerous studies relating the human electroencephalogram (EEG) to sensory input, attention, behavior, and various cognitive processes (Shagass, 1972). Many studies of EEG activity during nonlinguistic auditory input have been limited to the use of simple sounds such as pure tones. In a recent report, Wagner (1975a) re-viewed the limited literature relating human brain-waves to the perception of music and suggested that additional EEG studies might be helpful in increasing our understanding of the brain mechanisms underly-ing perception of complex musical stimuli.

The purpose of the present study was to determine if EEG measures of the electrical activity of the brain are systematically related to subjective reactions to musical stimuli. To our knowledge, the present study represents one of the few published demonstra-tions of significant relationships between subjective reactions to musical stimuli and EEG measures of brainwave activity.

METHOD

Subjects Twentyfour right handed undergraduate students from

Brandon University participated in the study. Twelve of the sub jects were advanced undergraduate majors drawn from the faculty of music. The remaining subjects were nonmusicians selected from an introductory psychology course. An equal number of males and females were represented in both groups. All potential

This study was supported by Brandon University President's NRC Grant 2374. Address requests for reprints to: J . L. Walker, Department of Psychology, Brandon University, Brandon, Manitoba, Canada, R7A 6A9. I wish to thank Professor Alan Ehnes from the Faculty of Music at Brandon University for assistance in conducting this study.

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subjects were given an initial screening, and any student report ing a preference for the left hand was not included in the study. The subjects ranged in age from IS to 32 years. The mean age of the musicians was 21.2 years, and the mean age of the non musicians was 21.S years.

Procedures EEG recordings were collected during three aural conditions,

including two musical conditions and a period of silence. The first musical stimulus consisted of a 1.63min recording of Mahler's Symphony No.5, fourth movement "Adagietto," final F major theme statement to end of movement. This slow and generally peaceful movement was scored for harp and strings and was from a recording by the Chicago Symphony Orchestra (London, CSA222S). The second musical condition was 1.75 min long and represented an instrumental interlude from "Gypsy" by Uriah Heap ("Uriah Heap," Mercury, SR6129). It consisted of a repetitive pattern in parallel fifths played on electric guitars with a heavy recurring rhythmic pattern on drum set and modal flavored blues solo on electric organ. Both musical selections were exclusively instrumental. The music stimuli were recorded once in the monaural mode onto magnetic tape and played to each subject at a constant comfortable listen ing level over a Realistic stethoscope headset. The silence condi tions consisted of the playing of a 2min segment of blank tape through the audio system and the earphones. The earphones were reversed for every other subject so that any asymmetries in the tape or earphones would be balanced over ears. The order of the stimulus conditions was also completely counterbalanced between subjects so that each stimulus appeared equally often on the first, second, and third stimulus trial.

Electrodes were attached over left and right hemisphere occipital lobe locations at 0, and 0, of the 1020 International Electrode Placement System. Recordings were bipolar, with each electrode referenced to the vertex electrode at Cz Prior to recording, the impedance of each electrode was tested, and any electrode showing an impedance of S kQ or larger was reapplied until the impedance was smaller than S kQ. The ground electrode was placed on the left ear lobe. All EEG recordings were done on a Grass Model 79C polygraph. Recording procedures are described in more detail elsewhere (Walker & Ehnes, Note I).

During the experiment, the subjects sat in an upright position in a recliner chair with their eyes closed. The subjects were housed in a sound-deadened room, and all recording instrumentation was

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located in an adjoining room. After each musical stimulus was presented, the experimenter reentered the experimental room and administered the subjective reaction scale.

EEG records were scored using the manual period analysis method developed by Sulg (1969). Manual scoring of the EEG tracings was done independently of the scoring for the subjective response scales so that the experimenter was blind to the subjective responses during all EEG scoring. Because of practical restric-tions, it was not possible to analyze all of the EEG records collected during the course of the study. The results described below represent an analysis of EEG frequencies during the first 5 sec, the 5 sec following the midpoint, and the last 5 sec of each stimulus condition. In all, a total of 15 sec of EEG tracings were analyzed for each subject at each recording site during each of the three aural conditions. Measures were collected describing the percentage of four basic EEG frequency classes. Percent beta represents percent time of 14-30-Hz activity, percent alpha cor-responds to percent time of 8-13-Hz activity, percent theta reflects 4-7-Hz activity, and percent delta represents slow 1-3-Hz EEG frequencies.

Immediately following the end of each musical stimulus, a rating scale was given to each subject, allowing them to evaluate a number of their subjective reactions to the music they had just heard. The rating scale consisted of eight scales with descrip-tive adjectives on both ends of the scale. The bipolar adjectives were separated by a l3-cm line, and subjects were asked to put a slash through each line at a point which corresponded to their subjective reaction. One end of each scale was arbitrarily defined as the zero point, and the maximum score on each scale was 13 cm. The distance of the slash from the zero end of the scale was measured in millimeters and expressed the person's score on that scale. The following items were included on the rating sheet: "1. How familiar was the musical selection you have just heard? (Put a slash through the line at a point which corresponds to your general evaluation of the familiarity of the music.): un-familiar-familiar; 2. How would you describe the music you have just heard? (Put a slash through each line at a point which corresponds to your general impression.): comforting-disturbing; depressing-exciting; happy-sad; unpleasant-pleasant. 3. During the music I: listened atter.tively to the music-played little attention to the music. 4. I personally found the music to be: irritating-soothing; 5. The music made me feel more: relaxed-tense.

At the completion of the study, the eight EEG indices and the scores on all eight rating scales for each subject were punched onto computer cards and a Pearson product moment correla-tion matrix was computed using computer program BMDI2D (Dixon, 1973). Several correlational matrices were computed in this manner, including the matrix for intercorrelations be-tween measures on all subjects to the classical music, inter-correlations for all subjects for the rock music condition, the cor-

relational matrix for nonmusicans with musical condition collapsed, and also the matrix for musicians across both music conditions.

RESULTS

Classical Music Table 1 presents correlations between subjective

reactions to the classical music and EEG percent activity times in each bandwidth during the classical music. Slow-wave delta activity over the left occipital site showed a correlation of r = - .424 (N = 23, P < .05) with scores on the "unpleasant"pleasant" scale. The sign of this correlation indicated that subjects giving ratings in the "unpleasant" direction tended to produce more delta activity at the left occipital site. Delta activity at the right occipital site showed a similar correlation with the "unpleasant-pleasant" scale (r = - .437, N = 23, p < .05). At both recording sites, high delta wave producers showed a tendency to rate the classical music as more unpleasant. The mean score on the "unpleasant-pleasant" scale was 10.7 (SO = 1.9). Since this scale was scored with "unpleasant" at the zero end of the scale, the average of 10.7 indicates a mean evaluation of the classical music toward the "pleasant" end of the scale.

Subjective reports of how attentive the subjects were to the music correlated significantly with four separate EEG measures. Theta activity at both left and right hemisphere occipital sites correlated signif-icantly with the "listened attentively to the music-payed little attention to the music" scale. The nega-tive sign of both of these correlations indicated that high theta producers tended to report paying less attention to the music. The mean response on the attentiveness scale was 10.1 (SO = 1.96). Subjective reports of attentiveness also were found to correlate significantly with the amount of delta and alpha activity over the right occipital site. The correlation between attentiveness and O2 delta was r = - .613 (N = 24, P < .01). The sign of the correlation indicated that high delta producers tended to report

Table 1 Correlations of Subjective Reactions and EEG Percent Activity Times During Qassical Music

paying less attention to the music. The correlating between right occipital alpha activity and reports of attentiveness was r = .418 (N = 24, p < .05). This correlation suggested that high attentiveness to the music was associated with increased alpha production.

In an attempt to determine if music-induced EEG changes were associated with sUbjective reactions, additional EEG scores were computed reflecting EEG percent activity time during music minus EEG percent activity time during silence. Table 2 presents the mean difference scores (music-silence) for all subjects to both the classical and rock music. The t tests reported in Table 2 tested the hypothesis that the mean difference between music and silence was zero. The matrix resulting from correlating the EEG difference score for classical music with the sub-jective reactions to the classical music is presented in Table 3. At the left occipital site, a statistically significant correlation of - .58 (N = 24, p < .01) indicated that the larger the difference between per-cent theta during the music as compared to silence, the more relaxed the subjects rated themselves. Six-teen subjects showed greater levels of theta activity during the classical music as compared to the silence

condition. The mean difference between percent theta during music minus percent theta during silence was 2.29 (SD = 5.8). The difference between 0, alpha during music and silence correlated significant-ly with Scale 2 ("comforting-disturbing"). This correlation (r = .40, N = 23), p < .05) indicated that ratings toward the "comforting" end of the scale were associated with larger differences in 0, alpha during music as compared to silence. Fifteen subjects had larger alpha times during silence than during music (Xd = - .499, SD = 9.64). Scale 2 also correlated significantly (r = - .64, N = 23, p < .01) with the beta difference at 0,. This negative-ly signed correlation indicated that larger beta differ-ences were associated with increased ratings of being disturbed by the music. Ten subjects showed more beta activity at 0, during the music as compared to during the silence (Xd = 2.18, SD = 8.34) . Six significant correlations were present for EEG measures at the right hemisphere occipital site. Both difference scores for O2 alpha and O2 beta correlated significantly with Scale 1 (unfamiliar-familiar). The correlation of - .55 (N = 24, p < .01) for change in percent alpha and Scale 1 indicated that greater differences in O2 alpha during music as compared to

Table 2 Mean Difference Scores Between Music and Silence for EEG Frequencies